Much better Duty cycle control using the 555 timer in an A-Stable mode of operation.
Many of you commented on my previous 555 video asking how to create a circuit that allows a “Duty Cycle” of 50% or less. i.e. making the On time equal to, or less than, the Off time.
If you have not seen my previous video, I suggest you take a look at that first by clicking the following link:-
https://youtu.be/3lEN6hEGUmE?si=2YMth54Ov4rNPY30
UPDATE:- I have now posted a new video explaining Capacitor Charge and Discharge timings, which can be found here:-
https://youtu.be/mllC-hiBepY?si=GKLhJfNhzj1pZE-2
Anyhow, in this follow-up video I show how, by simply adding a couple of diodes you have much greater control over the duty cycle. I also demonstrate how to adapt the circuit to make it a variable duty cycle or controllable PWM (Pulse Width Modulation) circuit.
The 555 calculation spreadsheet I put together for this video can be downloaded from here:-
🔗https://1drv.ms/f/c/10f323cd9840b5df/EspKJwBKTStGqnxSNc_afKoB5deboy8ssQj1CPaqEQcMaA?e=IEUkGn
If you are interested in the handy configurable Resistor boards I utilised you can purchase them from Amazon here:-
🔗https://amzn.to/3RYiX75
For more information about Potentiometers see one of my previous videos here:-
🔗https://youtu.be/XngaWUy4NP8?si=AE3uQhorrneV4_dj
⏱️Timeline
-------------------
00:00:00 – Introduction
00:00:25 – Recap Previous 555 Video
00:01:28 – Charge & Discharge Timings
00:02:40 – Problem with Standard A-stable circuit.
00:03:10 – 555 Calculator (On/Off/Frequency & Duty Cycle)
00:04:40 – The solution.
00:05:55 – New Calculations
00:06:53 – Breadboard Layout of Circuit 1
00:07:59 – Oscilloscope Output of Circuit 1
00:10:03 – Circuit 1 Summary
00:10:53 – Variable Duty Cycle 1st Option
00:11:15 – Variable Duty Cycle Using Potentiometer
00:11:55 – Breadboard Layout Circuit 2
00:12:39 – Oscilloscope Output of Circuit 2
00:13:32 – Wrap Up
Correction:
10:05 the t1 & t2 results should both be 0.01525, not 0.0165 Seconds.